Some idiotic german 'invented' a way to 'save trees'. By converting your attachments to .wwf format - a special .pdf format that blocks printing. While this may be a great feature to block printing of contracts etcetera if you're running a malicious company, most people simply don't want this.
So the big question is: How do I block .wwf files?
In /etc/postfix/main.cf uncomment or add the following line
header_checks = pcre:/etc/postfix/header_checks
Then edit /etc/postfix/header_checks and add the following line:
/Content-Disposition: .*\.wwf"/ REJECT Please don't send .wwf files.
Attachment blocking in exchange is usually performed by a virusscanner/spamfilter. You could use for example Trend Micro or GFI to block .wwf files.
Depending on your setup, you could use amavisd-new, mailscanner or procmail to block out .wwf files.
To block attachments with qmail, you'll need Simscan. Simscan is a simple program that enables the qmail smtpd service to reject viruses, spam, and block attachments during the SMTP conversation so the processing load on the email system is kept to a minimum. The project is open source and uses other open source components. Small, very efficient and written in C.© GeekLabInfo Blocking .wwf attachments is a post from GeekLab.info. You are free to copy materials from GeekLab.info, but you are required to link back to http://www.geeklab.info